Field
Exemplary embodiments of the present disclosure relate generally to honeycomb structures, and to ceramic honeycomb particulate filters and substrates comprising a multi-layer outer skin layer exhibiting improved thermal expansion compatibility with the underlying honeycomb body, enhanced iso-static strength of the honeycomb structure, and improved manufacturing process times.
Technical Background
Particulate filters and substrates with large diameters may be difficult to manufacture to the tight dimensional requirements set by original equipment manufacturers (OEMs) and the supply chain due to unpredictable drying and firing shrinkage. Consequently, a cold set ceramic cement may be used to form an exterior skin of a honeycomb monolith including honeycomb monoliths formed by honeycomb segments. The cold set ceramic cement is mixed and applied to a fired, contoured or segmented substrate and the wet skin is afterward allowed to dry either under ambient conditions or by convective or microwave drying at elevated temperatures. The dried part is then ready to receive a catalyst coating and any further downstream processing if required.
Present skin designs embody conflicting physical property requirements between the final application and the intermediate processing and handling. In service, the material must have a low thermal expansion and high thermal shock resistance (low elastic modulus) to endure severe thermal gradients. To achieve these properties, high porosity and weak bonding are desired for maximum skin flexibility. To withstand shipping, handling and/or processing (including extreme pH exposure during catalyzation), high strength and chip/abrasion resistance are desired. To achieve these properties, low porosity and strong bonding between the skin and the ceramic body are sought for maximum skin strength.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention as claimed and therefore it may contain information that does not form any part of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.